The discovery of potent nonstructural protein 5A (NS5A) inhibitors with a unique resistance profile-Part†2.

In ongoing studies towards novel hepatitis C virus (HCV) therapeutics, inhibitors of nonstructural protein 5A (NS5A) were evaluated. Specifically, starting from previously reported lead compounds, peripheral substitution patterns of a series of biaryl-linked pyrrolidine NS5A replication complex inhibitors were probed and structure-activity relationships were elucidated. Using molecular modelling and a supercritical fluid chromatographic (SFC) technique, intramolecular H-bonding and peripheral functional group topology were evaluated as key determinants of activity and membrane permeability. The novel compounds exhibited retained potency as compared with the lead compounds, and also showed promising results against a panel of resistance viruses. Together, the results of the study take us a step closer towards understanding the potency of daclatasvir, a clinical candidate upon which the compounds were based, and to designing improved analogues as second-generation antiviral agents targeting NS5A.

Non-traditional antibacterial screening approaches for the identification of novel inhibitors of the glyoxylate shunt in gram-negative pathogens.

Antibacterial compounds that affect bacterial viability have traditionally been identified, confirmed, and characterized in standard laboratory media. The historical success of identifying new antibiotics via this route has justifiably established a traditional means of screening for new antimicrobials. The emergence of multi-drug-resistant (MDR) bacterial pathogens has expedited the need for new antibiotics, though many in the industry have questioned the source(s) of these new compounds. As many pharmaceutical companies' chemical libraries have been exhaustively screened via the traditional route, we have concluded that all compounds with any antibacterial potential have been identified. While new compound libraries and platforms are being pursued, it also seems prudent to screen the libraries we currently have in hand using alternative screening approaches. One strategy involves screening under conditions that better reflect the environment pathogens experience during an infection, and identifying in vivo essential targets and pathways that are dispensable for growth in standard laboratory media in vitro. Here we describe a novel screening strategy for identifying compounds that inhibit the glyoxylate shunt in Pseudomonas aeruginosa, a pathway that is required for bacterial survival in the pulmonary environment. We demonstrate that these compounds, which were not previously identified using traditional screening approaches, have broad-spectrum antibacterial activity when they are tested under in vivo-relevant conditions. We also show that these compounds have potent activity on both enzymes that comprise the glyoxylate shunt, a feature that was supported by computational homology modeling. By dual-targeting both enzymes in this pathway, we would expect to see a reduced propensity for resistance development to these compounds. Taken together, these data suggest that understanding the in vivo environment that bacterial pathogens must tolerate, and adjusting the antibacterial screening paradigm to reflect those conditions, could identify novel antibiotics for the treatment of serious MDR pathogens.

Pyridone methylsulfone hydroxamate LpxC inhibitors for the treatment of serious gram-negative infections.

The synthesis and biological activity of a new series of LpxC inhibitors represented by pyridone methylsulfone hydroxamate 2a is presented. Members of this series have improved solubility and free fraction when compared to compounds in the previously described biphenyl methylsulfone hydroxamate series, and they maintain superior Gram-negative antibacterial activity to comparator agents.